Lash adjusting device



A ril 30, 1963 J. D. FAIRCHILD LASH ADJUSTING DEVICE Filed Nov. 15, 1961 INVENTOR. (JOHN D. FA/RCH/LD ATTORNEY United States Patent Q 3,087,477 LASH ADJUSTING DEVICE John D. Fairchild, Ferndale, Mich, assignor to Earl A. Thompson Manufacturing Company, a corporation of Michigan Filed Nov. 13, 1961, Ser. No. 151,227 2 Claims. (Cl. 123-90) This invention relates to mechanical lash adjusting systems for engine valve actuating trains, and more particularly to a type of spring-loaded lash adjuster wherein potential lash is deliberately introduced into the valve train by fully compulsive means which is extremely simple and rugged and which is not adversely afiected by inertia conditions during engine operation.

Recent developments in the mechanical lash adjuster field for modern automotive engines have taught the desirability of providing a force-multiplying mechanism of the annular or rotary wedge variety having an inherently self-locking angle considerably below the critical friction angle. This mechanism is shifted in a direction to introduce potential lash while the valve is unse-ated to insure positive, firm seating of the valve; it is then biased in the opposite direction to wipe out such potential lash while the valve is seated to insure quiet operation and full lift on the following unseating stroke. Furthermore, because of the diverse operating conditions of modern automotive engines which render the niceties of critical friction requirements wholly unreliable, the means for shifting the wedge device in the direction of increased lash while the train is loaded must constitute a positive one-way drive including a fully compulsive reaction connection as well as a positive driving connection. For truly successful use in mass production high speed engines, moreover, such positive driving means must be extremely simple for both economic and maintenance reasons as well as being free from adverse influence by inertia forces which change with engine speeds Accordingly, it is an object of the present invention to provide a lash adjusting device including a purely one-way abutment drive arrangeemnt for a self-locking rotary wedge which is positive in action because of compulsive driving and reaction connections and absence of critical frictional balances, is extremely simple of structure involving relatively few moving parts, and is designed to minimize adverse influences produced by changing inertia forces.

A more particular object of the present invention is to provide a pair of co-axially positioned and relatively rotatable adjusting members having mating rotary inclined ramp surfaces on their mutually contacting ends embodying a self-locking helix angle extending through a full circle, which members are compulsively rotated relative to one another on the valve opening stroke to introduce potential lash into the valve train and biased in the opposite direction after the valve seats to preclude actual lash from the train.

Further objects and advantages of the present invention will be apparent from the following detailed description, with reference to the accompanying drawings in which like reference characters refer to the same parts throughout the several views, and in which:

FIGURE 1 is a sectional elevational view with parts 3,087,477 Patented Apr. 30, 1963 ice broken away of a rocker arm and a fulcrum embodying the lash adjuster of this invention;

FIGURE 2 is a top view of such a rocker arm and fulcrum;

FIGURE 3 is an elevational view of the one-way drive adjusting member of such a lash adjuster; and

FIGURE 4 is an exploded perspective view of the pair of adjusting members of such a lash adjuster.

Referring in more particularity to the drawings, a rocker arm 10 which may be of the trough-shaped or dished yariety is fulcrumed intermediate its end about a downwardiyfacing semi-spherical fulcrum 12 positioned on an upright stud 14 fixed in the engine 16. Means forming a push rod abutment 18 at one end of the rocker arm cooperate with a push rod 20 operated by the conventional rotary cam, not shown. Means forming a valve stem abutment 22 at the other end of the rocker arm cooperate with the stem of a conventional valve 24- which is biased upwardly against its seat, not shown, by means of a valve seating spring 26.

The lash adjusting device of this invention serves to vary the elfective length of the valve actuating train by controlling the upward and downward adjustment of the rocker arm fulcrum 12 in relation to its supporting stud 14. To this end, the stud 14 may include axially extending splines 28 around its mid-portion and threads 30 on its upper end. The fulcrum member 12 may include a central aperture embodying splines 32 which mate with the splines 28 on the stud to position the fulcrum for axial motion and against rotary motion thereon. The upper surface of the fulcrum 12 may include a rotary inclined ramp surface 34 embodying a self-locking helix angle extending through a full circle. A hole 36 in the upper poriton of the member 12 is adapted to receive one end of a lash take-up spring, explained below.

To control the axial position of the fulcrum member 12 on the stud 14, another adjusting member 38 comprising a one-Way driving arrangement may be rotationally positioned on the stud 14. The member 38 is held against upward axial motion by means of a washer 40 and a pair of lock nuts 42 positioned on the threads 30 of the stud. Adjustment of the nuts 42 serves to effect semi-permanent adjustment in the effective length of the valve actuating train. The member 38 is thus positioned by means of an aperture 44 for rotary motion on the stud 14, and includes a downwardly depending annular body portion 46 which terminates at its lower end in a rotary inclined ramp surface 47 mating with the surface 34 of the fulcrum member. A hole 48' in the upper body portion of the adjusting member may be provided to receive the other end of a lash take-up spring, explained below. An actuating arm 50 integral with the adjusting member 38 may extend radially and normal to the axis fro-m the upper portion of the adjusting member 38, and through a distance which carries its end beyond the lateral confines of the upwardly extending side wall of the rocker arm 10.

A cut-out portion 52 of one side wall of the rocker arm forms an actuating shoulder 54 in abutting engagement with the side of the arm 50. Clockwise oscillatory motion of the rocker arm about its fulcrum 12 (FIGURE 1) brings the shoulder 54 into abutting relationship with the arm 50 which drives the adjusting member 38 in a clockwise direction (FIGURE 2) about the stud 14. The cutout portion 52 of the rocker arm wall is of sufficient extent so that it will not interfere with the new, shifted position of the operating arm 50 as the rocker arm returns in a counterclockwise direction about its fulcrum (FIGURE 1) on the valve seating stroke.

A coiled torsion or lash take-up spring 56, having its upper end anchored in the hole 48 in the adjusting member 38 and its lower end anchored in the hole 36 of the fulcrum member 12, is provided to bias the upper of the two adjusting members in a direction which translates the lower one downwardly on the stud in the direction of decreased lash. This spring is too weak to turn the member 38 in relation to the rotationally fixed member 12 when the valve train is loaded by the force of the valve seating spring 26; however, the spring is operative when the valve is seated to drive the member 38 counterclockwise (FIGURE 2) to decrease the effective length of the valve actuating train.

In operation, with the parts positioned as shown in the drawings, the lash adjusting mechanism will operate once on each open-ing and closing cycle of the valve in response to the driving cam. As the cam forces the push rod upwardly to pivot the rocker arm in a clockwise direction about its fulcrum on the valve opening stroke, the abutment shoulder 54 will contact the abutment arm 50 and rotate the adjusting member 38 in a direction which allows upward translation of the fulcrum 12 to introduce an increment of potential lash into the train. As the rocker arm pivots in the opposite direction on the valve closing stroke, the abutment members move away from each other because the self-locking angle of the mating helix surfaces 34, 47 hold the member 38 in its shifted position. This self-locking feature of the helix angle retains the recently introduced increment of potential lash in the actuating train until the valve is fully and positively at rest on its seat, as can be understood. After the valve seats, the cam still has several more degrees of falling contour because of the shortened effect of the train. Thus, as soon as the valve seats, the lash take-up spring 56 becomes operative to drive the adjusting member 38 in a counterclockwise direction (FIGURE 2) to :translate the fulcrum member 12 downwardly as fast as the receding cam contour permits to wipe out any actual lash in the train. In normal operation, this will swing the arm abutment 50 only part of the way back towards the shoulder abutment 54. On the next valve opening stroke, the shoulder 54 will pick up the arm 50 at this mid-point and again move it to the extreme position to introduce lash to insure proper valve seating.

Thus, a lash adjusting device has been disclosed which serves, by means of a single pair of positive acting abutments forming a fully compulsive driving connection and the splined stud forming a fully compulsive reaction connection, to shift an inherently self-locking rotary wedge through a variable distance to introduce a corresponding amount of potential lash into the train. This is done during the last portion 'of each valve opening stroke, such lash being retained on the valve closing stroke by the self-locking character of the wedge or force-multiplying mechanism until the valve seats, at which point the lash take-up spring operates to increase the effective length of the train as fast as the receding cam contour permits. The. amount of potential lash removed by this spring during normal warmed-up operation will shift the forcemult-iplying mechanism through only par-t of the available lash eliminating distance, thus only a corresponding increment of potential lash will be introduced by the oneway drive abutments on the next opening stroke. Thus, the increment or amount of potential lash will vary with the lengths of the parts relative to each other and to the engine. Enough extra travel of the force-multiplying mechanism may be provided to compensate for wear of the parts.

Furthermore, the extreme simplicity of the device renders it available for mass production purposes, and

the placement of the partsparticularly of the forcemultiplying mechanism including its operating abutmentminimizes adverse influences caused by momentum and inertia forces during high speed engine operation.

While the above described embodiment constitutes a preferred mode of carrying out this invention, many other forms might be adopted within the scope of the actual in?- vention, which is variously claimed as:

1. A lash adjusting system of the mechanical type fora valve operating train of an engine comprising in com-- 'bin-ation therewith a pair of co-axially positioned and relatively rotatable" adjusting members having mating rotary inclined" ramp surfaces on their mutually contacting ends embodying a helix angle and extending through no more:

than a full circle,

one of the adjusting members being secured against' rotation relative to the other in a direction which would vary the effective length of the train and the other adjusting member being rotatable in one di-- rection and return through a limited stroke to decrease and increase, respectively, the effective length of the train by a predetermined amount,

a single pair of one-way drive abutments movable toward and away from one another between spaced and engaged relationships in response to valve opening and valve closing motion of the train, respectively, one of the abutments being associated with the other adjusting member and the other abutment being located to engage the one abutment part way through the valve opening motion of the train and thereafter compulsively rotate the other adjusting member in the one direction from a mid-stroke position through the distance required to reach the limit of its stroke to create a corresponding amount of potential lash in the train,

the helix angle of the ramp being inherently self-locking against the force of valve train load to retain such amount of potential lash in the train during valve closing motion of the train as the abutments disengage and move away from one another,

and a lash take-up spring having insufficient force to rotate the other adjusting member while the train is loaded and connected to rotate the other adjusting member in the return direction away from its stroke limit to a mid-stroke position through the distance: required to remove actual lash from the train as the load on the train is relieved by seating of the valve.

2. A lash adjusting system of the mechanical type for a valve operating train of an engine comprising in com-- bination therewith a fulcrum,

a trough-shaped rocker arm mounted for oscillatory motion about the fulcrum to transfer motion between.

a push rod and a valve stem,

an adjustable mounting for the fulcrum including an;

upright stud,

a pair of co-axially positioned and relatively rotatable adjusting members on the stud and having mating rotary inclined ramp surfaces on their mutually con-- tacting ends embodying a helix angle extending: through no more than a full circle,

one of the adjusting members being associated with the fulcrum and being secured against rotation relative to the other in a direction which would vary the effective length of the train and the other adjusting member being rotatable in one direction and return through a limited stroke to decrease and increase, respectively, the effective length of the train by a predetermined amount,

a single pair of one-way drive abutments movable toward and away from one another between spaced and engaged relationships in response to valve opening and valve closing motion of the train, respectively, one of the abutments being associated with the other 6 adjusting member and the other abutment being locatloaded and connected to rotate the other adjusting ed on the rocker arm to ngage the O e abu m member in the return direction away from its stroke P y through the Valve Waning motion of the limit to a midast-roke position through the distance train and thereafter compulsively rotate the other ad- [required to remove actual lash fr the train as the justing member in the one direction ir-om a mid- 5 stroke position through the distance required to reach the limit of its stroke to create a corresponding amount of potential lash in the train,

load on the train is relieved by seating of the valve.

References Cited in the file of this patent the helix :angle of the ramp being inherently self-locking UNITED STATES PATENTS against the :force of valve train load to retain such 10 2132251 4 Goodwin June 22 1943 amount of potential lash in the train during valve 2642048 Russell June 16 1953 closing motion of the train as the abutments disen- 2743713 Russell May 1956 gage and move away firom one another, 2934051 Drew A. r 1960 and a lash take-up spring having insufiicient force to 3009450 g 'gg T 1961 rotate the other adjusting member while the train is 15 

2. A LASH ADJUSTING SYSTEM OF THE MECHANICAL TYPE FOR A VALVE OPERATING TRAIN OF AN ENGINE COMPRISING IN COMBINATION THEREWITH A FULCRUM, A TROUGH-SHAPED ROCKER ARM MOUNTED FOR OSCILLATORY MOTION ABOUT THE FULCRUM TO TRANSFER MOTION BETWEEN A PUSH ROD AND A VALVE STEM, AN ADJUSTABLE MOUNTING FOR THE FULCRUM INCLUDING AN UPRIGHT STUD, A PAIR OF CO-AXIALLY POSITIONED AND RELATIVELY ROTATABLE ADJUSTING MEMBERS ON THE STUD AND HAVING MATING ROTARY INCLINED RAMP SURFACES ON THEIR MUTUALLY CONTACTING ENDS EMBODYING A HELIX ANGLE EXTENDING THROUGH NO MORE THAN A FULL CIRCLE, ONE OF THE ADJUSTING MEMBERS BEING ASSOCIATED WITH THE FULCRUM AND BEING SECURED AGAINST ROTATION RELATIVE TO THE OTHER IN A DIRECTION WHICH WOULD VARY THE EFFECTIVE LENGTH OF THE TRAIN AND THE OTHER ADJUSTING MEMBER BEING ROTATABLE IN ONE DIRECTION AND RETURN THROUGH A LIMITED STROKE TO DECREASE AND INCREASE, RESPECTIVELY, THE EFFECTIVE LENGTH OF THE TRAIN BY A PREDETERMINED AMOUNT, A SINGLE PAIR OF ONE-WAY DRIVE ABUTMENTS MOVABLE TOWARD AND AWAY FROM ONE ANOTHER BETWEEN SPACED AND ENGAGED RELATIONSHIPS IN RESPONSE TO VALVE OPENING AND VALVE CLOSING MOTION OF THE TRAIN, RESPECTIVELY, ONE OF THE ABUTMENTS BEING ASSOCIATED WITH THE OTHER ADJUSTING MEMBER AND THE OTHER ABUTMENT BEING LOCATED ON THE ROCKER ARM TO ENGAGE THE ONE ABUTMENT PART WAY THROUGH THE VALVE OPENING MOTION OF THE TRAIN AND THEREAFTER COMPULSIVELY ROTATE THE OTHER ADJUSTING MEMBER IN THE ONE DIRECTION FROM A MIDSTROKE POSITION THROUGH THE DISTANCE REQUIRED TO REACH THE LIMIT OF ITS STROKE TO CREATE A CORRESPONDING AMOUNT OF POTENTIAL LASH IN THE TRAIN, THE HELIX ANGLE OF THE RAMP BEING INHERENTLY SELF-LOCKING AGAINST THE FORCE OF VALVE TRAIN LOAD TO RETAIN SUCH AMOUNT OF POTENTIAL LASH IN THE TRAIN DURING VALVE CLOSING MOTION OF THE TRAIN AS THE ABUTMENTS DISENGAGE AND MOVE AWAY FROM ONE ANOTHER, AND A LAHS TAKE-UP SPRING HAVING INSUFFICIENT FORCE TO ROTATE THE OTHER ADJUSTING MEMBER WHILE THE TRAIN IS LOADED AND CONNECTED TO ROTATE THE OTHER ADJUSTING MEMBER IN THE RETURN DIRECTION AWAY FROM ITS STROKE LIMIT TO A MID-STROKE POSITION THROUGH THE DISTANCE REQUIRED TO REMOVE ACTUAL LASH FROM THE TRAIN AS THE LOAD ON THE TRAIN IS RELIEVED BY SEATING OF THE VALVE. 